i2c: at91: don't account as iowait

iowait is for blkio [1]. I2C shouldn't use it.

[1] https://lkml.org/lkml/2014/11/3/317



Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: stable@kernel.org